Dynamic inventory that sets ansible_python_interpreter for localhost correctly, even within a virtualenv

localhost.py

#!/usr/bin/env python

# Generate a "localhost" entry dynamically that uses a local connection and
# the same Python interpreter that's being used to execute this inventory
# script, which will work properly within a virtualenv.

import argparse
import json
import os
import sys

parser = argparse.ArgumentParser(description='Ansible dynamic inventory.')
group = parser.add_mutually_exclusive_group()
group.add_argument('--list', action='store_true', help='List host groups')
group.add_argument('--host', metavar='HOSTNAME', help='Return host vars')

args = parser.parse_args()

host_vars = {
    'ansible_connection': 'local',
    'ansible_python_interpreter': sys.executable
}

if args.list:
    groups = {
        'local': {
            'hosts': ['localhost'],
            'vars': host_vars
        }
    }

    json.dump(groups, sys.stdout)
elif args.host:
    if args.host == 'localhost':
        json.dump(host_vars, sys.stdout)
    else:
        print '{}'
else:
    parser.print_help(sys.stderr)
    sys.exit(1)